1. Field of the Invention
The invention relates to an apparatus for the detection of a specifically reacting substance in a test liquid. In this apparatus a test strip is involved comprising an analytical system. The apparatus of the invention is specifically intended for home use or use by nonprofessional organisations, whereby the test is usually carried out by laymen or non skilled people.
In the state of the art there are various types of test strips for detecting specifically reacting substances. Such a test strip can for example, when provided with a certain colour indicator, be used for measurement of the pH of the test liquid. However, for the detection of specifically reacting substances by an immunoassay, test strips with a more complicated analytical system are required. Upon contact with such a test strip, which is preferably made of a porous material, the test liquid, possibly containing the specifically reacting substance to be detected, is transported along the test strip by capillary action. The test strip usually contains different reagent zones comprising for example specific reactants for the substance to be detected. One of these reactants is provided with a label, preferably a coloured label which can be observed visually. The test liquid subsequently passes the various reagent zones, whereby different immunological reactions will take place. The complexes formed will finally be bound by a reagent on the detection spot and will be visible by the label involved. Such strips are now commercially available.
2. Description of the Related Art
EP-A-0 183 442 discloses a chromatographic device comprising a housing and a strip of bibulous material non-removably confined in the housing. The inner walls of the housing contain means for supportively confining the strip in the housing. This means supportively confines the strip in the housing so that the front and back of the strip are essentially free from contact with the walls of the housing. The bottom end of the housing contains means for enabling a portion of the strip to contact the liquid medium. The housing additionally contains means for visually observing the strip.
EP-A-291 194 discloses an analytical test device which consists of a hollow casing of rigid material which is impermeable to moisture, and contains in the casing a dry porous support. The support is connected to the outside of the casing in such a way that a liquid test sample can be applied to the support. The sample then migrates through the support, on which immunological reactions take place and provide a visible analytical result in a particular zone of the support. In order to be able to observe the latter, openings are also provided in the casing. Direct labelling materials such as, for example, gold sol particles are used for visualization.
EP-A-0 349 215 discloses a test cell for detection of a ligand in a liquid sample, comprising an elongate casing for a permeable material. This permeable material is capable of transporting an aqueous solution disposed within the casing and comprises a receptor for the ligand. Receptor-coupled coloured particles are used for detection of the ligand. Observation of the test site is permitted by a hole or transparant section of the casing.
The known apparatuses for the detection of specifically reacting substances comprise a test strip, with an analytical system, enclosed in a housing. This housing is almost hermetically sealed, so that, after reaction of the test liquid with the reagents on the test strip, evaporation of the test liquid is seriously delayed or even prohibited. As a consequence the reagents may diffuse back to the detection spot, which will give rise to incorrect results.